The invention relates to a cathode ray tube having an envelope comprising a screen and an electron gun situated inside the envelope oppostie to the screen and having at least two electrodes, said electrodes being provided coaxially on the inner wall of a glass tube in adjoining places having diameters which differ for each electrode. The invention furthermore relates to a method of manufacturing a cathode ray tube.
A cathode ray tube of the kind mentioned in the opening paragraph is known from U.S. Pat. No. 4,304,586.
Conventionally, an electron gun is constructed from a beam-forming part consisting of a cathode and a few electrodes which serve to generate, modulate and pre-focus an electron beam, and a prefocusing lens which ensures that the beam is focused on the screen of the tube in which the gun is present.
Such a lens in a conventional gun also consists of a number of electrodes. All these electrodes are usually held together by means of a number of insulation rods.
As a reuslt of the present-day development towards electron guns of smaller dimensions and electron beams having greater brightness, the requirements as regards the tolerances in the spacings between the electrodes mutually and the alignment of the electrodes become more stringent.
In addition, it is desired to simplify the construction of the electrode system used.